Image Editor 2D gizmo name?
TL;DR The UV translate tool uses GIZMO_GT_arrow_3d.

The gizmo groups that are used for the tools in the UV editor can be seen in _defs_image_uv_transform (space_toolsystem_toolbar.py).
The ID name of the gizmo group is IMAGE_GGT_gizmo2d_translate which is implemented in space_image.c. It uses ED_widgetgroup_gizmo2d_xform_no_cage_callbacks_set, which in turn calls ED_widgetgroup_gizmo2d_xform_callbacks_set  that stores gizmo2d_xform_setup as function for the setup. Should the setup function be called this also results in gizmogroup2d_init being executed. Its return value is a GizmoGroup2D that is used to set gizmos for the operators through WM_gizmo_operator_set. The gizmo types that are returned by gizmogroup2d_init in a GizmoGroup2D are GIZMO_GT_arrow_3d, GIZMO_GT_cage_2d and GIZMO_GT_button_2d.
These functions are implemented in transform_gizmo_2d.c.